1. Field of the Invention
The present invention relates to a deactivating device for a locking mechanism of a pretensioner, for use in a pretensioner for forcibly retracting an occupant-restraining webbing of a webbing retractor by being operated, so as to activate or deactivate the locking mechanism of the pretensioner as an operation lever is moved.
2. Description of the Related Art
A seat belt apparatus is adapted to restrain a vehicle occupant by means of a webbing when a vehicle suddenly decelerates. As the clearance between the webbing and the occupant decreases, the time required to restrain the occupant also decreases. For this reason, pretensioners for allowing the webbing to be applied closely around the occupant by forcibly pulling the webbing in the direction of retraction when the vehicle suddenly decelerates, as well as webbing retractors equipped with the pretensioner, have been proposed (e.g., Japanese Utility Model Application Publication No. 58-6430 and Japanese Utility Model Application Laid-Open Nos. 55-8556 and 55-45306).
When the vehicle suddenly decelerates, the pretensioner (and the webbing retractor) of this type is operated to rotate a webbing takeup shaft in the retracting direction. However, since it is necessary to ensure that the pretensioner (and the webbing retractor) is not operated when the pretensioner is assembled onto the vehicle body or is detached therefrom, the pretensioner is provided with a locking mechanism for preventing operation thereof.
The locking mechanism of the pretensioner is arranged such that, for example, as a shaft connected to the locking mechanism is rotated, the pretensioner is set in an operative state or in an inoperative state. If the shaft is rotated by an operation lever, the locking mechanism can be activated or deactivated.
Although, as described above, the locking mechanism of the pretensioner is activated or deactivated as the shaft is rotated by the operation lever, when, for instance, the pretensioner (and the webbing retractor) is assembled onto the vehicle body or is transported in a state in which it is detached from the vehicle body, if the pretensioner is handled carelessly and a large impact or the like acts on the operation lever, there is the possibility of the shaft from becoming rotated undesirably due to the impact or the like acting on the operation lever, thereby deactivating the locking mechanism unnecessarily. Therefore, it is necessary to adopt a measure for reliably maintaining the pretensioner in the deactivated state even in such a case.